Backlight unit and liquid crystal display device comprising the same

ABSTRACT

According to one embodiment, a backlight device includes a support frame including a first frame body including a pair of first frame members and a second frame member connected to respective ends of the first frame members and a second frame body being separate from the first frame body, which connects other respective ends of the first frame members to each other, a reflective sheet on the support frame, a light guide on the reflective sheet within the support frame, an optical sheet on the light guide, and a light source unit in the support frame. The light source unit includes a wiring board on the second frame body and a light source on the wiring board, opposing an incidence surface of the light guide.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2016-230169, filed Nov. 28, 2016, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a backlight device anda liquid crystal display device comprising the same.

BACKGROUND

In recent years, liquid crystal display devices are widely used as adisplay device of smartphones, tablet computers, vehicle-navigationsystems, etc. In general, a liquid crystal display device comprises aliquid crystal display panel and a backlight device overlaid on the rearsurface of the liquid crystal display panel and illuminates the liquidcrystal display panel. The backlight device includes a reflective layer,a light guide, an optical sheet, a light source unit which irradiateslight which enters the light guide. The reflective layer, light guideand optical sheet are stacked one on another. The backlight devicefurther includes a case (bezel) made from a metal plate, whichaccommodates these members. The light source unit includes a wiringboard and a plurality of light sources, for example, light-emittingdiodes (LEDs) mounted on the wiring board.

In recent years, as display areas have increased, there has been acontinual demand for the frames of liquid crystal display devices tobecome ever narrower and the liquid crystal display devices to becomeever thinner.

SUMMARY

The present disclosure generally relates to a backlight device and aliquid crystal display device.

According to one embodiment, a backlight device includes a support frameincluding a first frame body including a pair of first frame members anda second frame member connected to respective ends of the first framemembers and a second frame body being separate from the first framebody, which connects other respective ends of the first frame members toeach other, a reflective sheet on the support frame, a light guide onthe reflective sheet within the support frame, an optical sheet on thelight guide, and a light source unit in the support frame. The lightsource unit includes a wiring board on the second frame body and a lightsource on the wiring board, opposing an incidence surface of the lightguide.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a display surface side of a liquidcrystal display device of an embodiment.

FIG. 2 is a perspective view showing a rear surface side of the liquidcrystal display device.

FIG. 3 is an exploded perspective view of the liquid crystal displaydevice.

FIG. 4 is an exploded perspective view of a backlight device of theliquid crystal display device.

FIG. 5 is a partially enlarged perspective view showing a part of asupport frame of the backlight device.

FIG. 6A is a perspective view showing a light source unit of thebacklight device.

FIG. 6B is a perspective view showing an optical unit of the backlightdevice according to a modification.

FIG. 7 is a perspective view showing a light source-side end portion ofthe liquid crystal display device.

FIG. 8 is a cross sectional view showing the light source-side endportion of the liquid crystal display device exploded along line A-A ofFIG. 1.

FIG. 9 is a cross sectional view showing a long side end portion of theliquid crystal display device exploded along line B-B of FIG. 1.

FIG. 10 is a cross sectional view showing a light source-side endportion of a liquid crystal display device of another embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, abacklight device comprises: a support frame comprising a first framebody including a pair of first frame members opposing each other and asecond frame member connected to respective ends of the first framemembers, and a second frame body formed to be separate from the firstframe body, which connects other respective ends of the first framemembers to each other; a reflective sheet on a first surface of thesupport frame; a light guide on the reflective sheet within the supportframe; an optical sheet on the light guide; and a light source unit inthe support frame, comprising a wiring board fixed on the second framebody and a light source on the wiring board, opposing an incidencesurface of the light guide.

Note that the disclosure is presented for the sake of exemplification,and any modification and variation conceived within the scope and spiritof the invention by a person having ordinary skill in the art arenaturally encompassed in the scope of invention of the presentapplication. Furthermore, a width, thickness, shape, and the like ofeach element are depicted schematically in the figures as compared toactual embodiments for the sake of simpler explanation, and they do notlimit the interpretation of the invention of the present application.Furthermore, in the description and figures of the present application,structural elements having the same or similar functions will bereferred to by the same reference numbers and detailed explanations ofthem that are considered redundant may be omitted.

Embodiments

FIGS. 1 and 2 are perspective views showing, respectively, a displaysurface side and a rear side of a liquid crystal display deviceaccording to an embodiment. FIG. 3 is an exploded perspective view ofthe liquid crystal display device.

A liquid crystal display device 10 can be incorporated into, forexample, various kinds of electronic devices, such as smartphones,tablet computers, mobile phones, notebook PCs, portable game consoles,electronic dictionaries, television sets and car-navigation systems, tobe used.

As shown in FIGS. 1, 2 and 3, the liquid crystal display device 10comprises an active-matrix liquid crystal panel 12, a transparent coverpanel 14 overlaid on a display surface 12 a, which is one flat surfaceof the liquid crystal panel 12 and configured to cover the entiredisplay surface 12 a, and a backlight device 20 provided to face therear surface, which is the other flat surface of the liquid crystalpanel 12.

The liquid crystal panel 12 comprises a rectangular plate shaped firstsubstrate SUB1, a rectangular plate shaped second substrate SUB2 opposedto the first substrate SUB1, and a liquid crystal layer LQ held betweenthe first substrate SUB1 and the second substrate SUB2. Acircumferential portion of the second substrate SUB2 is attached to thefirst substrate SUB1 with a frame-shaped sealing member SE. On thesurface of the second substrate SUB2, a polarizer PL2 is attached toform the display surface 12 a. A polarizer PL1 is attached on a rearsurface (a back of the liquid crystal panel 12) of the first substrateSUB1.

The liquid crystal panel 12 comprises a rectangular display area (activearea) DA for displaying images, and a rectangular frame area(non-display area) ED provided around the display area DA. The displayarea DA is provided in a region inner side of the sealing member SE asthe liquid crystal panel 12 is seen in plan view (which is a view of theliquid crystal panel from the normal direction of the display surface ofthe panel). The liquid crystal panel 12 is a transmissive liquid crystalpanel having a transmissive display function of displaying imaging byselectively transmitting or modulating the light from the backlightdevice 20 in the display area DA. The liquid crystal panel 12 may have astructure provided for the lateral electric field mode which mainlyutilizes a lateral electric field substantially parallel to a surface ofthe substrate, or a structure provided for the vertical electric fieldmode which mainly utilizes a vertical electric field crossing the mainsurface of the substrate.

In the example illustrated, a flexible printed circuit board (FPC) 23 isjoined to a short edge-side end of the first substrate SUB1 and extendsfrom the liquid crystal panel 12 outward. On the FPC 23, semiconductordevices including a driver IC 24 are mounted as signal supply sourceswhich supply signals necessary to drive the liquid crystal panel 12. Asshown in FIG. 2, the FPC 23 is folded over along a short edge of thefirst substrate SUB1 and overlaid on a bottom surface of the backlightdevice 20.

As shown in FIGS. 1 and 3, the cover panel 14 is formed into arectangular plate shape from glass or an acrylic transparent resin, forexample. The cover panel 14 has dimensions (width and length) greaterthan those of the liquid crystal panel 12 and an area greater than thatof the liquid crystal panel 12 in planar view. The lower surface (rearsurface, surface on a liquid crystal panel side) of the cover panel 14is adhered to the display surface 12 a of the liquid crystal panel 12with an adhesive layer made from a transparent adhesives or adhesive,for example, and covers the entire display surface 12 a.

A frame-shaped light-shielding layer RS is formed on the lower surfaceof the cover panel 14. In the cover panel 14, a region other than theregion which opposes the display area DA is shielded by thelight-shielding layer RS. The light-shielding layer RS may be formed onthe upper surface (outer surface) of the cover panel 14. Note that thecover panel 14 may be omitted according to the use status of the liquidcrystal display device 10.

The backlight device 20 comprises a rectangular support frame 22, andoptical members and a light source unit 50 provided in the support frame22. The backlight device 20 is disposed to oppose the rear surface ofthe liquid crystal panel 12 and attached to the rear surface with aframe-shaped adhesive member, for example, a double-stick tape TP1.

As shown in FIG. 3, in this embodiment, the widths of the side edges ofthe rectangular frame-shaped non-display area ED are all the same orsubstantially the same. More specifically, widths WL1 and WL2 of thenon-display area ED, which correspond to a pair of long side edges ofthe display area DA are equal to each other (WL1=WL2). Note here thatthe widths WL1 and WL2 are referred to as the distance from the boundarybetween the display area DA and the non-display area ED to the end edgeof the first substrate SUB1 (and the second substrate SUB2) in the longside edges of the display area DA. Moreover, of a pair of short sideedges of the display area DA, the width of the non-display area ED on aside where the FPC 23 is provided (which may be referred to as themounting side, hereafter) is defined as WS1, and the width of thenon-display area ED on a short side edge opposite thereto is defined asWS2. Here, WS1/WS2≤2.0 is preferable. More preferably, WS1/WS2≤1.5, andstill more preferably, WS1/WS2≤1.0 can be adopted. Here, the width WS1is defined as the distance from the boundary between the display area DAand the non-display area ED to the end edge of the first substrate SUB1in the short-edge side on the mounting side. The width WS2 is defined asthe distance from the boundary of the display area DA and thenon-display area ED to the end edge of the first substrate SUB1 (and thesecond substrate SUB2) in the short-edge side opposite to the mountingside.

Moreover, the above-described structures should preferably satisfy:WL1=WL2<1.5 mm and WS2<1.5 mm, and more preferably, WL1=WL2<1.0 mm andWS2<1.0 mm. Furthermore, in any of these structures, WL1=WL2=WS2 can beadopted.

With the above-described conditions, this embodiment can achieve such astructures that the width WS1 of the mounting side of the liquid crystalpanel 12 can be remarkably narrowed than the conventional technique,i.e., the width WS1 of the non-display area ED on the mounting side canbe made substantially equal to that of the other regions of thenon-display area ED. Thus, such a liquid crystal panel 12 can beprovided with a narrowed frame in which the widths of all the sides ofthe non-display area ED which surrounds the display area DA are allsubstantially the same.

Next, the backlight device 20 will be described in more detail. In orderto achieve a significantly narrowed frame in the non-display area ED ofthe mounting side, a structure in the light-source side portion of thebacklight device 20 is different from that of the conventionaltechniques. Moreover, in order to further thin the structure, the case(bezel) formed into a box shape by pressing sheet metal is omitted fromthe backlight device 20.

FIG. 4 is an exploded perspective view of the backlight device 20. FIG.5 is a perspective view schematically showing the support frame. FIG. 6Aincludes perspective views of the light source unit, each including apartially expanded view thereof. FIG. 7 is a perspective view of thelight source-side end portion of the liquid crystal display device. FIG.8 is a cross sectional view of the liquid crystal display device takenalong line A-A in FIG. 1. FIG. 9 is a cross section view of the longedge-side portion of the liquid crystal display device taken along lineB-B in FIG. 1.

As shown in FIG. 4, the backlight device 20 comprises a flat rectangularsupport frame 22, a reflective sheet attached to a first surface (lowerend surface) of the support frame 22, a plurality of optical membersarranged in the support frame 22 and a light source unit 50 supported bythe support frame 22.

As shown in FIGS. 4 and 5, the support frame 22 comprises, for example,a U-shaped resin frame (first frame body) 24 molded form a syntheticresin and a metal member (second frame body) 26 fixed to the resin frame24 to form one side portion of the support frame 22. The resin frame 24includes a pair of long frame members (first frame members) 25 a and 25b opposing each other and a first short frame member (second framemember) 25 c connected to the one end portion of each of the long framemembers 25 a and 25 b, as one integrated body. The resin frame 24comprises a first surface (upper end surface) 24 a and a second surface(lower end surface) 24 b on an opposite side thereto. A stepped portion24 c, which is one step lower, is formed in an inner circumference ofthe first surface 24 a. The stepped portion 24 c is continuously formedin the long frame members 25 a and 25 b and the first short frame member25 c all around its full length.

As shown in FIG. 9, the long frame members 25 a and 25 b and the firstshort frame member 25 c are formed, for example, to have a width W1 of0.4 to 0.5 mm and a height (thickness) T1 of about 0.3 to 0.5 mm. Thestep difference (depth) T2 of the stepped portion 24 c is madesubstantially equal to the thicknesses of two films, i.e., a filmthickness of a first optical sheet OS1 and that of a second opticalsheet OS2, which will be described later.

As shown in FIGS. 4, 5 and 7, the metal member 26 is fixed to the endportions of the long frame members 25 a and 25 b. In other words, themetal member 26 forms the second short frame member which opposes thefirst short frame member 25 c. The metal member 26 is, for example, astainless plate (SUS board) having a thickness of 0.3 mm. The metalmember 26 is bent to have an L-shaped cross section. Thus, the metalmember 26 includes an oblong first plate portion 26 a and an oblongsecond plate portion 26 b perpendicularly to the first plate portion 26a, as an integrated body.

Both longitudinal end portions of the first plate portion 26 a areattached to the first surface 24 a of the end portions of the long framemembers 25 a and 25 b and both longitudinal end portions of the secondplate portion 26 b are attached respectively to the end portions of thelong frame members 25 a and 25 b with an adhesive member TP7 such as adouble-stick tape. As shown in FIG. 7, a width W2 of the second plateportion 26 b is greater than the height T1 of the resin frame 24. Withthis structure, the second plate portion 26 b extends over the secondsurface 24 b of the resin frame 24.

The width of the support frame 22 is substantially equal to a width ofthe first polarizer PL1 of the liquid crystal panel 12. The length ofthe support frame 22 is slightly greater than a length of the firstpolarizer PL1.

It should be noted that wordings such as “identical” and “equal” indimensions are not to positively exclude errors inevitable in themanufacture of the actual product or previously allowing a tolerance forsuch errors at the time of design, and include, from this point of view,those which can be the to be approximately identical to each other. Thesame applies to the description after this.

As shown in FIGS. 4, 7, 8 and 9, the backlight device 20 includes, asoptical members, a reflective sheet RE having a rectangular shape inplanar view, a light guide LG, a plurality of, for example, two, firstoptical sheets OS1 and second optical sheets OS2. The number of opticalsheets is not limited to two, but three or more sheets may be used. Forexample, as the first optical sheets OS1, a diffusion sheet is employed,whereas a prism sheet is employed as the second optical sheets OS2.

The reflective sheet RE has external dimensions substantially equal tothe external dimensions of the resin frame 24. The reflective sheet REhas a thickness of 200 μm or less, preferably, 50 to 90 μm and areflectivity of 90% or higher, preferably, 95% or higher. Three sideedge portions of the reflective sheet RE are attached to the secondsurface 24 b of the resin frame 24 with an adhesive member TP3 such as adouble-stick tape. Thus, the reflective sheet RE covers substantiallythe entire surface of the second surface 24 b. One short side edge ofthe reflective sheet RE opposes the metal member 26 with a gaptherebetween.

The light guide LG comprises a first main surface S1, a second mainsurface S2 opposing the first main surface S1 and a plurality of, forexample, a pair of long-side surfaces and a pair of short-side surfaces,which connect side edges of the first main surface S1 and the secondmain surface S2 to each other. In this embodiment, one short-sidesurface constitutes the incidence surface EF of the light guide LG. Thelight guide LG has, for example, a thickness of about 0.23 to 0.32 mm.Moreover, the light guide LG is formed from, for example, a resin suchas polycarbonate, an acrylic or silicon resin.

The light guide LG has dimensions (length and width) slightly smallerthan the internal dimensions of the support frame 22 and slightly largerthan the display area DA of the liquid crystal panel 12 in plan view.The light guide LG is arranged in the support frame 22 and placed on thereflective sheet RE while the second main surface S2 opposes thereflective sheet RE. Thereby, the first main surface (emission surface)S1 of the light guide LG is located substantially parallel to thereflective sheet RE and the incidence surface EF is locatedsubstantially perpendicular to the reflective sheet RE.

As shown in FIG. 8, an incidence-side end of the light guide LG projectsfrom a border BD between the display area DA and the non-display area EDof the liquid crystal panel 12 towards the metal sheet member 26. Thedistance between the incidence surface EF of the light guide LG and thesecond plate portion 26 b of the metal sheet member 26 is preferably 1.0mm or less, more preferable 0.8 mm or less, and still more preferably,0.5 mm or less. In the conventional backlight devices, the distancebetween the incident surface of the light guide and the side wall of thecase corresponds to the above-described distance. Conventionally, thedistance is set to about 3.0 mm to 4.0 mm. As compared to theconventional structure, the distance between the metal sheet member 26of the support frame 22 and the light guide LG in this embodiment isremarkably less. Then, the light source unit 50 is provided between themetal sheet member 26 and the light guide LG.

A light source-side end REa of the reflective sheet RE projects over theborder BD and the incidence surface EF towards the light source. Withthis structure, the end REa of the reflective sheet RE opposes to thesecond plate portion 26 b of the metal sheet member 26 with a gap, aswell as part of the light sources of the light source unit 50.

As shown in FIGS. 5 and 6A, the light source unit 50 comprises, forexample, a belt-shaped wiring board 52 and a plurality of light sourcesmounted in lines on the wiring board 52. As light sources,light-emitting elements, for example, light-emitting diodes (LEDs) 54are employed.

A flexible printed circuit board (FPC) is used for the wiring board 52.That is, the wiring board 52 includes an insulating layer formed frompolyimide or the like and a conductive layer such as a copper foil,formed on the insulating layer. The conductive layer is patterned toform a plurality of contact pads 55 and wiring lines 56.

The wiring board 52 includes a belt-shaped mounting portion (mountingregion) 52 a and a plurality of, for example, three belt-shaped lead-outportions (wiring regions) 52 b extending substantially perpendicularlyfrom one side edge of the mounting portion 52 a, all integrated as onebody. A length L1 of the mounting portion 52 a is substantially equal toa length of the incidence surface EF of the light guide LG. The lead-outportions 52 b are arranged to be spaced from each other in alongitudinal direction of the mounting portion 52 a.

The contact pads 55 are formed in the mounting portion 52 a and arearranged in a longitudinal direction of the mounting portion 52 a. Thewiring lines 56 extend respectively from the contact pads 55 to thelead-out portions 52 b and are routed on the lead-out portions 52 b.

As shown in FIG. 6A, the LEDs 54 used here are each a top-view type LED.Each LED 54 comprises a substantially rectangular parallelepiped case(package) 60 formed of a resin, for example. An upper surface of thecase 60 forms a light-emitting surface 62 and a bottom surface of thecase 60, which is located on an opposite side to the light-emittingsurface 62, forms a mounting surface. Contact terminals 63 are providedon the bottom surface of the case 60.

Note that each LED 54 is formed into substantially a rectangularparallelepiped, but the shape is not limited to this. For example, theLED 54 may comprise projections and recesses in side surfaces, or may beformed into a curvy shape.

As to each LED 54, the bottom of the case 60 is mounted on the mountingportion 52 a of the wiring board 52, and thus the contact terminals 63are electrically connected to the contact pads 55. The light-emittingsurface 62 of the LED 54 is set substantially parallel to the wiringboard 52, and the LED 54 emits light from the light-emitting surface 62in a direction substantially perpendicular to the wiring board 52.

The LEDs 54 are mounted on the mounting portion 52 a so that thelongitudinal direction of the case 60 is aligned with the longitudinaldirection of the mounting portion 52 a. The width W1 of the mountingportion 52 a is 1.1 to 1.5 times the width W of the LED 54. In thisembodiment, the light source unit 50 includes a plurality of LEDs 54,the number of which may vary according to the width of the display areaDA. The number of the LEDs installed is about 2.5 to 3 times that of theconventional structure of the same display area. The LEDs 54 arearranged in one row on the mounting portion 52 a from one longitudinalend to the other of the mounting portion 52 a.

Note that in this embodiment, an arrangement pitch P of the LEDs 54 isset to about 1.1 to 1.5 times of the length L of each LED 54 in thealigning direction, and a gap D of each adjacent pair of LEDs 54 is setto about 10% to 50% of the length L of the LEDs 54. Conventionally, thearrangement pitch of LEDs is set to two times or more the length of theLEDs. In this embodiment, the gap D between the LEDs 54 is set narrowerthan conventional cases, and thus the region of uneven brightness, whichmay be generated between each adjacent pair of light sources, can benarrowed.

In this embodiment, a belt-shaped fixing tape (light-shielding tape) TP2as a second adhesive member for fixing and positioning each LED 54 isadhered onto a side surface of each of the LEDs 54. The fixing tape TP2is used such that about a half of the region in a width direction isadhered to each LED 54, and a remaining half of the region is adhered tothe light guide LG. The fixing tape TP2 comprises a belt-shaped basematerial 55 a formed of, for example, polyethylene terephthalate (PET),and an adhesive layer 55 b or sticker layer formed on at least onesurface of the base material 55 a. Further, at least one of the basematerial 55 a and the adhesive layer 55 b is colored in black with, forexample, fine black particles, black ink or the like. Thus, the fixingtape TP2 forms a light-shielding member with light shielding property.The fixing tape TP2 employed here is not limited to one continuous tape,but may be of a plurality of divided fixing tapes.

The number of LEDs 54 mounted may be increased or decreased as needed.When LEDs longer than the length L1 are used, the number of LEDs to bemounted may be decreased. According to a modification shown in FIG. 6B,the length L1 of the LEDs 54 is set to about 4 to 5 times that of theLEDs 54 shown in FIG. 6A. The width W1 of the mounting portion 52 a ofthe wiring board 52 is 1.1 to 1.5 times the width W1 of the LEDs 54. Thearrangement pitch P of the LEDs 54 is set to about 1.1 to 1.5 times thelength L1 of the LEDs 54, and the gap D between adjacent pairs of LEDs54 is about 10% to 50% of the length L1 of the LEDs 54.

As shown in FIGS. 4 and 8, the light source unit 50 configured asdescribed above is arranged in the support frame 22. The mountingportion 52 a of the wiring board 52 and the LEDs 54 are arranged betweenthe incidence surface EF of the light guide LG and the second plateportion 26 b of the metal sheet member 26. The light-emitting surfaces62 of the LEDs 54 oppose or abut against the incidence surface EF. Themounting portion 52 a of the wiring board 52 is attached to the innersurface of the second plate portion 26 b by an adhesive member, forexample, a double-stick tape TP4. The mounting portion 52 a opposes theincidence surface EF via the LEDs 54 interposed therebetween.

The LEDs 54 each comprises four side surfaces perpendicularly crossingthe light-emitting surface 62. Of the four side surfaces, a side surface54 b located on a liquid crystal panel 12 side is arranged to besubstantially flush with the second main surface S2 of the light guideLG. The fixing tape TP2, more specifically, about a half of the regionin its width direction, is adhered on the surface side 54 b of the LED54, and the rest of the half is adhered onto an incidence surface-sideend of the first main surface S1. Thus, the LEDs 54 are fixed to thelight guide LG via the fixing tape TP2, and the light-emitting surface62 is positioned to abut against the incidence surfaces EF of the lightguide LG. Further, the fixing tape TP2 shields the side surface 54 bside of each LED 54 to inhibit light from leaking from the LEDs 54.

According to this embodiment, the base material 55 a of the fixing tapeTP2 is provided to abut against the inner surface of the first plateportion 26 a of the metal sheet member 26. The fixing tape TP2 isinterposed between the first plate portion 26 a and the LEDs 54 and heldto attach to the LEDs 54 and the light guide LG.

According to this embodiment, as the first optical sheet OS1 and thesecond optical sheet OS2, a light-transmissive diffusion sheet and alight-transmissive prism sheet, formed from, for example, a syntheticresin such as polyethylene terephthalate, are used. As shown in FIGS. 4,8 and 9, the first optical sheet OS1 is formed into a rectangular shapehaving external dimensions larger than the internal dimensions of theresin frame 24 and smaller than the external dimensions thereof. Thelength of the first optical sheet OS1 is less than that of the resinframe 24 and that of the light guide LG.

The first optical sheet OS1 is overlaid on the first main surface S1 ofthe light guide LG, to cover substantially the entire first main surfaceS1. The three side edge portions of the first optical sheet OS1,excluding the short edge on the light source unit 50 side, are placed onthe stepped portion 24 c of the resin frame 24.

The second optical sheet OS2 is formed into a rectangular shape havingdimensions identical to those of the first optical sheet OS1. The secondoptical sheet OS2 is overlaid on the first optical sheet OS1, to coversubstantially the entire first optical sheet OS1. The edge portions ofthe second optical sheet OS2 are attached to the edge portions of thefirst optical sheet OS1 with a frame-shaped adhesive member, forexample, a double-stick tape TP5. The double-stick tape TP5 is coloredin black with, for example, fine black particles, black ink or the like.Thus, the double-stick tape TP5 has a light-shielding property.

The three side edge portions of the second optical sheet OS2, excludingthe short edge on the light source unit 50 side, and the double-sticktape TP5 are placed on the stepped portion 24 c of the resin frame 24.Thus, the upper surface (the surface on the liquid crystal panel 12side) of the second optical sheet OS2 is located to be flush with thefirst surface 24 a of the resin frame 42. As shown in FIG. 8, the shortedge portions of the first optical sheet OS1 and the second opticalsheet OS2 and the double-stick tape TP5 extend to the non-display areaED and are substantially aligned with the light source-side short edgeof the first polarizer PL1 of the liquid crystal panel 12. Further, theshort edge is located just in front of the incident surface EF of thelight guide LG to oppose the fixing tape TP2 with a slight gaptherebetween. That is, the double-stick tape TP5 having light-shieldingproperty is disposed in the vicinity of the LED 54, and can contributeto the shielding of the light leaking from the case of the LED 54.

As shown in FIGS. 3, 8 and 9, the rectangular frame-shaped firstadhesive member, that is, for example, the double-stick tape TP1, isattached on the upper end surface of the support frame 22. Three edgeportions of the double-stick tape TP1 each have a width equal to thewidth W1 of the resin frame 24 and are stacked and attached on the firstsurface 24 a of the resin frame 24 and the edge portions of the secondoptical sheet OS2. With the double-stick tape TP1, the second opticalsheet OS2 and the first optical sheet OS1 are fixed and positioned tothe resin frame 24. The other one edge TP1 a of the double-stick tapeTP1 has a width substantially equal to the width of the first plateportion 26 a of the metal member 26 and is overlaid and attached on theentire first plate portion 26 a.

At least the edge TP1 a of the double-stick tape TP1 should preferablyhave a light-shielding property. According to this embodiment, thedouble-stick tape TP1 is colored in black with, for example, fine blackparticles, black ink or the like. Thus, the double-stick tape TP1 has alight-shielding property. The edge TP1 a of the double-stick tape TP1opposes the LEDs 54 via the metal member 26. Thus, the double-stick tapeTP1 can contribute to the shielding of the light leaking from the caseof the LED 54.

As described above, on the liquid crystal panel 12 side of the LED 54,the light-shielding fixing tape TP2, double-stick tape TP5 anddouble-stick tape TP1 are provided, and the light leaking from the caseof LED 54 can be shield in triple by these light-shielding members.

As shown in FIGS. 2 and 8, according to this embodiment, the backlightdevice 20 may comprise a heat-radiating sheet 70. The heat-radiatingsheet 70 is formed from, for example, a highly heat conductive materialsuch as graphite. The heat-radiating sheet 70 is laid on the locationopposing the light source unit 50 and attached onto an outer surface ofthe second plate portion 26 b of the metal member 26 and the backsurface of the reflective sheet RE. The heat generated by the LEDs 54propagates to the metal member 26 having large heat capacitance throughthe wiring board 52 and further from the metal member 26 to theheat-radiating sheet 70. Further, part of the heat generated from theLEDs 54 directly propagates to the heat-radiating sheet 70. The heatwhich has propagated to the heat-radiating sheet 70 radiates to theoutside from the heat-radiating sheet 70, and part of the heat istransmitted from the heat-radiating sheet 70 to the reflective sheet RE,which radiates to the outside from the reflective sheet RE. Thus, anexcessive increase in temperature of the light sources of the lightsource unit 50 can be suppressed, thereby making it possible to preventa local increase in temperature in the backlight device 20.

The backlight device 20 configured as above is attached on the back ofthe liquid crystal panel 12 with the frame-shaped double-stick tape TP1.As shown in FIGS. 2, 7 to 9, the resin frame 24 is attached to on theedge portions of the first polarizer PL1 with the double-stick tape TP1.The metal member 26 of the support frame 22 is stuck to the back of thefirst substrate SUB1 with the double-stick tape TP1. The second opticalsheet OS2 opposes the entire first polarizer PL1 with a gaptherebetween. Further, the light source unit 50 is located to overlapthe non-display area ED.

In the liquid crystal display 10 configured as above, the box-shapedcase (bezel) where the optical members and the light source unit areaccommodated is omitted from the backlight device 20. By omitting thecase, the display can be downsized by the thickness of the case and thewidth of the frame portion. Moreover, one edge portion of the supportframe 22 is formed from the metal member 26, and therefore themechanical strength of the support frame 22 can be enhanced, making itpossible to stably support the structural members of the backlightdevice 20, especially those on the light source side where a number ofmembers are densely concentrated, by the support frame 22. Morespecifically, the light source unit 50, which relatively heavy, isattached to the metal member 26, and thus the light source unit 50 canbe firmly supported at a predetermined position. Furthermore, thestructural members of the backlight device 20 is attached to the liquidcrystal panel 12 via the support frame 22 or the double-stick tape(adhesive member) TP1. Thus, the structural members of the backlightdevice 20 are held in the liquid crystal panel 12, securing thestrength. As a result, even if the conventional case is omitted, theliquid crystal display 10 exhibits a desired strength as a whole. Thelight source unit 50 employs top-view LEDs 54, thereby making itpossible to arrange the wiring board 52 of the light source unit 50 tooppose the incident surface EF of the light guide LG while interposingthe LEDs 54 therebetween. With this structure, the wiring board 52 doesnot interfere with optical members such as the optical sheet OS and thelight guide LG or the display area DA of the liquid crystal panel 12,thereby making it possible to reduce the frame area ED on the lightsource side in great deal.

Moreover, according to this embodiment, the fixing tape (second adhesivemember) TP2 is attached continuously over the side surfaces of the LEDs54 and the second main surface S2 of the light guide LG, to position andfix the LEDs 54 with respect to the light guide LG. Thus, the LEDs 54can be held while the light-emitting surfaces thereof abut against theincident surface EF of the light guide LG, and thus the optical axis ofeach LED 54 can be accurately adjusted with respect to the incidentsurface EF. Furthermore, the fixing tape TP2 has a light-shieldingproperty, and therefore it can shield the light leaking from the sidesurface of the case of the LEDs 54 and also the light leaking from theboundary between each of the light-emitting surfaces of the LEDs 54 andthe light guide LG. Thus, the light leaking from the light sources canbe suppressed more reliably, thereby improving the display quality ofthe display device. Furthermore, the light-shielding double-stick tapeTP5 and double-stick tape TP1 are provided to be adjacent to or overlaidon the LEDs 54. With this structure, the light leaking from the sidesurface of the case of the LEDs 54 and also the light leaking from theboundary between each of the light-emitting surfaces of the LEDs 54 andthe light guide LG can be more reliably shielded by the double-sticktapes TP1 and TP5.

As described above, according to this embodiment, a backlight devicewhich can be thinned and reduce the width of the frame, and a liquidcrystal display device comprising the backlight device can be provided.

Now, a liquid crystal display device according to another embodimentwill be explained. In the other embodiment described below, the samestructural elements as those of the first embodiment are denoted by likereference numbers, detailed description thereof being omitted orsimplified. Structural elements different from those of the firstembodiment are mainly explained in detail.

FIG. 10 is a cross section of a light source-side end of a liquidcrystal display according to another embodiment. This embodiment isdifferent from the one described in the positions where the LEDs 54 ofthe light source unit 50 are arranged. More specifically, as shown inFIG. 10, the light source unit 50 is attached to a metal member (secondframe member) 26 of the support frame 22. The light source unit 50comprising a wiring board 52 and a plurality of LEDs 54 mounted on thewiring board 52. The wiring board 52 is attached to a second plateportion 26 b of the metal member 26 with a double-stick tape TP4. TheLEDs 54 are located between an incident surface EF of the light guide LGand the wiring board 52. A light-emitting surface 62 of each of the LEDs54 opposes the incident surface EF or abuts against the incident surfaceEF. In this embodiment, the LEDs 54 are arranged in such positions thatlower side surfaces thereof (side surfaces side opposite to the liquidcrystal panel 12) are substantially flush with a second main surface S2of the light guide LG. End portions of the LEDs 54, which are on alight-emitting surface 62 side are mounted on a light source-side endREa of a reflective sheet RE.

A light-shielding tape TP2, for example, a double-stick tape, isattached as an adhesive member onto the first plate portion 26 a of themetal member 26. A part of light-shielding tape TP2 is attached onto thefirst main surface S1 of the light guide LG. Such a structure can beadopted that the light source unit 50 is attached to the metal member 26with the double-stick tape TP2. Note that the double-stick tape TP2 iscolored in black with, for example, fine black particles, black ink orthe like. Thus, the double-stick tape TP2 has a light-shieldingproperty. The edge TP1 a of the double-stick tape TP1 opposes the LEDs54 via the metal member 26. Thus, the double-stick tape TP1 cancontribute to the shielding of the light leaking from the case of theLEDs 54. Moreover, as shown in FIG. 10, the thickness of the light guideLG is slightly greater than the height of the LEDs 54. Here, the processof mounting LEDs 54 on the wiring board 52 is considered to involve anattachment error which is difficult to avoid during actual manufactureespecially in the height direction of the LEDs 54. However, theabove-described structure can cope with this kind of LED attachmenterror. Furthermore, above the LEDs 54, the light-shielding tape TP2 iscontinuously provided from the wiring board 52 over to the incidentsurface EF of the light guide LG. Therefore, even if such attachmenterror of LEDs 54 may occur, the leakage of light resulting from sucherror can be suppressed as much as possible.

In this embodiment, the other structure of the liquid crystal display 10is the same as that of the embodiment previously described. Further,with the back light device and the liquid crystal display of thisembodiment configured as above, an advantageous effect similar to thatof the previous embodiment can be obtained.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

Note that all the structures and production steps which can be carriedout by any modification and variation conceived within the scope andspirit of the invention by a person having ordinary skill in the artbased on each structural elements described in the embodiments arenaturally encompassed in the scope of invention of the presentapplication. Further, regarding the present embodiments, any advantageand effect which would be obvious from the description of thespecification or arbitrarily conceived by a skilled person are naturallyconsidered achievable by the present invention.

For example, the light-shielding member is not limited to a double-sticktape or a light-shielding tape, but the black printing, alight-shielding film or some other light-shielding layer may be used.The outer and inner shapes of the structural members of the liquidcrystal panel and backlight device are not limited to rectangular, butone or both of the outer and inner shapes may be polygonal, circular,elliptical or combination of any of these in plan view. The materials ofthe structural members are not limited to those described in the exampleprovided above, but may be selected from various types. The liquidcrystal panel is not limited to a flat type, but may be partially orentirely curved.

Further, in the embodiments, the U-shaped first frame body 24 is formedfrom a resin and the second frame body 26 fixed to the first framemember 24 is from a sheet metal. But, such a structure may be adaptedthat these materials are switched from one another, or both of thesemembers are formed from a resin or a metal.

What is claimed is:
 1. A backlight device comprising: a support framecomprising a first frame body including a pair of first frame membersopposing each other and a second frame member connected to respectiveends of the first frame members, and a second frame body formed to beseparate from the first frame body, which connects other respective endsof the first frame members to each other and opposes to the second framemember; a reflective sheet on a first surface of the support frame; alight guide on the reflective sheet within the support frame; an opticalsheet on the light guide; and a light source unit disposed in thesupport frame and comprising a wiring board fixed on the second framebody and a light source on the wiring board, opposing an incidencesurface of the light guide.
 2. The backlight device of claim 1, whereinthe light guide comprises a first main surface which forms alight-emitting surface, a second main surface opposing the first mainsurface and the incident surface located between end portions of thefirst main surface and the second main surface, the second main surfaceopposes to the reflective sheet, and the incident surface opposes thesecond frame body with a gap therebetween, and the wiring board opposesthe incident surface while interposing the light source therebetween. 3.The backlight device of claim 2, wherein the first frame body comprisesa second surface opposing the first surface, and the second frame bodycomprises a first plate portion opposing the second surface of the firstframe body and a second plate portion opposing the incident surfacewhile interposing the light source unit therebetween.
 4. The backlightdevice of claim 3, further comprising a light-shielding member betweenthe light source and the first plate portion.
 5. The backlight device ofclaim 3, further comprising a first adhesive member stacked on thesecond surface of the first frame body and the first plate portion ofthe second frame body, wherein at least a portion of the first adhesivemember, which is located on the first plate portion has alight-shielding property.
 6. The backlight device of claim 5, whereinthe optical sheet includes a first optical sheet on the light guide anda second optical sheet on the first optical sheet, the second opticalsheet includes an end portion on a side of the light source unit, andthe end portion is attached to the first optical sheet with alight-shielding adhesive layer.
 7. The backlight device of claim 1,further comprising a heat-radiating sheet attached onto the second framebody and the reflective sheet.
 8. The backlight device of claim 1,wherein the reflective sheet comprises a light source-side end extendingover the incident surface of the light guide to a position opposing thelight source.
 9. The backlight device of claim 1, wherein the firstframe body is formed from a resin and the second frame body is formedfrom a metal.
 10. A liquid crystal display comprising: a liquid crystalpanel comprising a first substrate, a second substrate opposed to thefirst substrate and a liquid crystal layer between the first substrateand the second substrate; a backlight device opposed to the firstsubstrate, the backlight device comprising: a support frame comprising afirst frame body including a pair of first frame members opposing eachother and a second frame member connected to respective ends of thefirst frame members, and a second frame body formed to be separate fromthe first frame body, which connects other respective ends of the firstframe members to each other and opposes to the second frame member; areflective sheet on a first surface of the support frame; a light guideon the reflective sheet within the support frame; an optical sheet onthe light guide; and a light source unit disposed in the support frameand comprising a wiring board fixed on the second frame body and a lightsource on the wiring board, opposing an incidence surface of the lightguide.
 11. The liquid crystal display of claim 10, wherein the firstframe body comprises a second surface opposing the first surface, andthe second surface of the support frame is attached to the liquidcrystal panel via an adhesive member.
 12. The liquid crystal display ofclaim 10, further comprising a heat-radiating sheet attached onto thesecond frame body and the reflective sheet.
 13. The liquid crystaldisplay of claim 10, wherein the reflective sheet comprises a lightsource-side end extending over the incident surface of the light guideto a position opposing the light source.
 14. The liquid crystal displayof claim 10, wherein the first frame body is formed from a resin and thesecond frame body is formed from a metal.